Cloud Computing categorization Exposed

We have typically heard about following cloud computing categories:

• IaaS (Infrastructure as a Service)
• PaaS (Platform as a Service)
• SaaS (Software as a Service)

There are lots of definitions available for these, all are good but people get confused when cross-questioned regarding the boundaries of each category. All are closely overlapped. Recently i got a chance to read an article by Douglas K Barry that help me in drawing the clear boundary for these categories. Thought for sharing the knowledge to draw that boundary more explicit by highlighting the overlapped area.

If we write all layers that are required for deployment, the stack will be:

1. Deployed/hosted application/service: Email, Communication
2. Development tool, server management tool, db management tool, run-time execution
3. Operating System
4. Virtualization
5. Servers and storage
6. Network configuration, firewall, network security, load-balancer
7. Data center, physical storage

IaaS: consist of layer 3 to 7

PasS: consist of layer 2 to 7

SaaS: consist of layer 1 to 7

I hope this definition will help you in grasping these terminologies.